In certain applications, electrical devices or sensors are used to measure or detect various operating or performance parameters such as, for example, temperature, pressure, or acceleration. These devices can be actuators or electronic devices such as magnetic field sensors. Typically, the electrical functions of the devices are communicated to support electronics and/or some recording apparatus that allows an operator to monitor the parameters being measured by the sensors. In many instances, the device is provided with terminals which are simply connected to lead wires extending from the support electronics or recording apparatus.
Some electronic devices are made of multiple layers of semiconductor material. These devices or sensors typically include an interior operating unit. The electrical function of the unit may occur at various layers of the device which must be connected to the external electronics. For example, lead wires may be connected to interior terminals on one or more surfaces of the interior operating unit, and then fed through access holes in the layers to the outside of the device. However, when electrical functions are communicated from surfaces on opposite sides, for example, an upward and a downward surface, of the interior operating unit, wiring to the unit becomes inconvenient during the assembly process.
Some assembly processes use a xe2x80x9cflip-chipxe2x80x9d technique in which the inner terminals of the interior operating unit are presented on one surface. Patterns of conductor lines extend from the inner terminals up an insulated surface of a semiconductor layer that is adjacent to the interior operating unit to an outer surface of the semiconductor layer. It has been proposed to electrically connect the interior operating unit to the outside by using metal thin films that coat oxide-insulated holes of semiconductor layers positioned next to the interior operating unit. Such connections, however, introduce large capacitance coupling which can be troublesome, for example, for systems working at radio frequencies. Furthermore, extending the conductor lines through several layers is not easily accomplished.
The present invention implements a device which encloses an interior electrical or operating unit while facilitating the transmission of electrical signals from the interior unit to a location outside of the device. The interior unit can be hermetically sealed within the device to protect the unit from the outside environment. The device includes two or more internal terminals connected to the interior unit and provides respective conductive paths from the internal terminals to two or more outer terminals located on the outer surface of the device.
In one embodiment, a multi-layer device includes a lid, a core, and a base. The lid has a first outer terminal and a second outer terminal, and a first insulator having a first surface bonded to the lid. The insulator also includes a first inner terminal located on a second surface for connecting to an interior operating unit, and a first etch pit that electrically connects the first outer terminal to the first inner terminal, and a second etch pit that is electrically connected to the second outer terminal. The core has a first surface bonded to the second surface of the first insulating layer and includes a pillar electrically connected to the second etch pit of the first insulator. A second insulator includes a first surface bonded to a second surface of the core and a second inner terminal located on that first surface also for connecting to the interior operating unit. The second insulator also includes a third etch pit electrically connected to the second inner terminal, and a fourth etch pit electrically connected to the pillar. The device is also provided with a base having a cap electrically connected to the third and fourth etch pits. Accordingly, there is a first conductive path defined from the first outer terminal of the lid through the first etch pit to the first inner terminal, and a second conductive path defined from the second outer terminal of the lid through the second etch pit, the pillar, the fourth etch pit, the cap, and the third etch pit to the second inner terminal.
The lid, the base, and the core can be made of silicon, and the first and second insulators can be made of Pyrex. In some embodiments, the electrical unit is hermetically sealed within the device. The first and second outer terminals can be coated with a conductive metal such as, for example, gold or platinum. Additionally, the etch pits and the inner terminals can be made from a conductive metal.
In certain embodiments, the lid further includes a third outer terminal, the first insulator includes a fifth etch pit, and a portion of the core serves as a third inner terminal so that there is a third conductive path defined from the third outer terminal, through the fifth etch pit to the third inner terminal.
In other embodiments, the lid further includes a fourth outer terminal, the first insulator includes a sixth etch pit, the core includes a second pillar, the second insulator includes a seventh etch pit, and the base includes a fifth outer terminal. In such embodiments, a fourth conductive path is defined from the fourth outer terminal through the sixth etch pit, the second pillar, and the seventh etch pit to the fifth outer terminal. The fourth outer terminal can be electrical connected to a portion of the lid, and the fifth outer terminal can be electrically connected to a portion of the base so that the portions of the lid and base, and the fourth and fifth outer terminals serve as guard electrodes.
In another embodiment, a multi-layer device includes a lid, a core, and a base. The lid has a first terminal and a second terminal, and an inner surface with a first insulator. The core has a first surface bonded to the first insulator and a second surface bonded to a second insulator, and includes a pillar electrically connected to the second terminal. The base has an inner surface bonded to the second insulator and a portion being electrically connected to the pillar. The first terminal of the lid, as well as the base, are adapted for electrically connecting to an interior electrical unit positioned within the core so that there are conductive paths to the first and second terminals. The lid can include a third terminal in electrical contact with a portion of the core, and the portion of the core can be adapted for electrically connecting to the electrical unit.
In any of the embodiments described above, the device can include the interior operating unit which is electrically connected to the internal terminals.
Related embodiments of the invention include a device with a lid having a first outer terminal and a second outer terminal, a base, and an interior operating unit having a first inner terminal electrically connected through the lid to the first outer terminal, and a second inner terminal electrically connected through the lid to the second outer terminal. The interior operating unit is hermetically sealed between the lid and the base.
Other embodiments include methods of making a device for electrically connecting an electrical unit enclosed within the device to the outside of the device. The methods can include a photochemical etching process to form the outer terminals and the pillars. The lid, the base, and the core can be bonded to the insulators with an anodic bonding process or a solder bonding process. Multiple devices can be made from wafers of semiconductor and insulator material bonded together. The individual devices are sawed apart from the wafers to form the individual devices thereby physically isolating the pillar of each device.
Some embodiments of the invention may have one or both of the following advantages. The conductive paths can extend through multiple layers of a multi-layer structure. The conductive paths can be separated by wide air gaps, which introduce only a small capacitance.